Michael Baumgartner, the freshman state senator who is challenging Democrat Maria Cantwell for her U.S. Senate seat, has endorsed Initiative 502, which would make retail sales of marijuana legal.

WASHINGTON — Republican U.S. Senate hopeful Michael Baumgartner on Wednesday endorsed Initiative 502 to legalize retail sales of pot, calling the war on the illicit drug a matter of national security.

The freshman state senator, who is challenging Democrat Maria Cantwell, worked several years ago for a State Department program in Afghanistan to help farmers grow wheat instead of opium poppies.

He said his experience in Helmand province — and watching the U.S.-funded efforts to eradicate Mexican drug cartels — convinced him criminalizing marijuana for adults only enriches traffickers and takes law-enforcement efforts from pursuing organized crime.

It was eight months ago that the Legislature decided to leave it up to voters whether to legalize and tax the sale of pot to those 21 and over. Baumgartner said he waited until now to endorse the initiative in part to see how it would propose to guard against minors buying pot and other issues.

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Asked for Cantwell’s position, spokesman Kelly Steele emailed this: “While I remain a strong supporter of our state’s medicinal marijuana laws, I don’t believe it should be legalized for recreational purposes based on concerns expressed by law enforcement and the current drafting of the initiative. Whatever the result, I will honor the will of the voters’ decision in November.”

Both gubernatorial candidates, Democrat Jay Inslee and Republican Rob McKenna, also oppose the initiative.

Kyung Song: 202-383-6108